I have this Powermac that I purchased second hand. The guy told me there were issues with it, so I got it cheap. It is a G5 Dual 2.3GHz What happens is pretty odd... If you boot the G5 from being completely shutdown, it WILL NOT display video or POST (If that is correct terminology) but it does power on and the drives spin. It will boot EVERYTIME however, if you zap the PRAM. Never fails, you zap it and it will boot fine and run fine. I have run tech tool deluxe which came back with no errors. A bit more history... When i first got this, I reset the reset the SMU and zapped the PRAM, got it booted and ran Techtool deluxe. After it passing the tests, i decided to install Leopard. Leo installed fine, but i had somewhere to go so it went to sleep during the install and would not turn back on. So, I REPLACED THE CMOS BATTERY WITH A NEW ONE. That seemed to have helped (maybe?) As now, I can tell the computer to go to sleep and it will come out of it. But, if I TELL IT TO SHUT DOWN, IT WILL NOT BOOT UNLESS THE PRAM IS ZAPPED. Even more interestingly enough, I have configured it as a RAID 0 and one time while it was booted, I wanted to repair disk permissions. I clicked on the RAID partition and selected repair permissions and the thing Kernel panicked on me. I dont know what all of this means, but maybe someone could shed some light on what zapping the PRAM does exactly and what piece of hardware you are actually "zapping". Thanks in advance.